THE PRESENT INVENTION relates to a vehicle safety arrangement, and more particularly relates to a safety arrangement adapted to trigger a safety device that is actuated or deployed in response to a predetermined sensed parameter indicative of an accident situation.
An air-bag is one example of a safety device that is actuated or deployed in response to a predetermined sensed parameter, an air-bag being typically associated with a sensor responsive to deceleration of the vehicle which initiates inflation or deployment of the air-bag. Another example of a safety device that is actuated or deployed is a safety-belt pre-tensioner which, in response to a sensed impact of the vehicle, applies a substantial tension to a safety-belt.
It has been proposed previously to actuate a safety device by an arrangement which incorporates two switches, both switches having to be closed before the safety device is deployed or actuated. In one such arrangement, a first accelerometer, which may be associated with a processor which processes a signal from the accelerometer, generates an output signal which closes a first switch in response to a predetermined deceleration. The deceleration may be a level of deceleration experienced when the vehicle is undergoing xe2x80x9cemergencyxe2x80x9d braking.
A second accelerometer, which again may be associated with a processor adapted to process an output signal from the accelerometer, generates a signal when a second, higher level of deceleration is experienced, or a relatively long period of deceleration is experienced such as that experienced during the initial stages of an impact. An output from this accelerometer is utilised to close the second switch. Output signals must be provided by both of the accelerometers, and associated processors, before both switches are closed the safety device will be deployed.
If a switch is closed due to an error in one of the processors, it is unlikely that the other processor will, at the same time, have an error that will cause an inadvertent deployment of the safety device.
The present invention seeks to provide an improved safety arrangement.
According to this invention there is provided a safety arrangement for a motor vehicle, the safety arrangement for a motor vehicle, the safety arrangement comprising sensor means in the form of at least one sensor adapted to sense a parameter indicative of an accident situation, and a control system controlling a triggering circuit, the control system incorporating at least one processor connected to the sensor means and to the triggering circuit, the processor having an input pin for activating a non-maskable interrupt (NMI) routine, the triggering circuit being adapted to actuate or deploy a safety device in response to a predetermined command generated by the processor in response to a predetermined output from the sensor means, said command generated by the processor creating an input to the said input pin of the processor to start said NMI routine, said NMI routine serving to determine whether there are hardware and/or software faults that may invalidate the command, and to interrupt actuation or deployment of the safety device if any such fault is detected.
Thus, even though only one processor is used, there is only a very slight risk that the safety device will be activated inadvertently.
A xe2x80x9cnon-maskable interruptxe2x80x9d (NMI) routine is a routine that immediately interrupts any routine or process running in the processor and which cannot itself be interrupted or dis-activated by any other routine. A non-maskable interrupt routine may be dictated by the configuration of the hardware within an appropriate portion of the processor, this configuration being such that the NMI routine itself cannot be interrupted once it has commenced. By selecting the hardware configuration of this portion of the processor appropriately, the precise nature of the NMI routine can be designed so that the routine performs one or more desired functions.
The triggering circuit that forms a part of the invention may be constituted by an application specific integrated circuit which may incorporate two switches. The arrangement may be such that both switches have to be closed before the safety device can be actuated or deployed.
Preferably the sensor comprises at least one accelerometer.
Conveniently the sensor comprises a first accelerometer and a second accelerometer.
Preferably, there are two separate connections between the processor and the means to deploy the safety device, the safety device only being actuated or deployed if appropriate signals are provided on both said connections.
In one embodiment the processor is adapted to form a safeing algorithm to generate a signal indicating the possibility of an accident, and has means to perform a crash algorithm adapted to provide a signal indicating that an accident has occurred.
Conveniently one connection is provided to send high level commands comprising a plurality of digital words with the other connection sending a low level command.
Preferably one of the connections is connected to said pin.
Conveniently the second connection which provides a low level command is the connection connected to said pin.
Preferably both the low level and the high level connections are controlled by the crash algorithm, a terminal command on the high level connection being sent only after the said non-maskable interrupt routine has been completed.